PISTON AND CONNECTING ROD ASSEMBLY

Abstract: A piston and connecting rod (10) includes a connecting rod (11) supporting a piston (14). The connecting rod (11) has a piston end (13), with the piston (14) being supported on the connecting rod (11) so that it is moved away from the piston end (13) during pivoting of the connecting rod (11) in response to a predetermined angular movement of its crank end (12) so as to maintain the compression ratio during the combustion phase and increase the dwell period of the piston (14) prior to its descent.

Description: PISTON AND CONNECTING ROD ASSEMBLY Field of the Invention The present invention pertains to internal combustion engines and more particularly to a piston assembly incorporating a novel interconnection between piston and connecting rod. Background of the Invention Ignition in an internal combustion engine, takes place just prior to the piston reaching "top dead centre". Combustion takes place with considerable expansion of the mixture within the combustion chamber. It is advantageous for combustion to take place at as high a pressure as possible. Engines are usually designed to have a compression ratio of 8:1 to 9:1. However as the piston is descending combustion is still taking place and accordingly, pressure within the combustion chamber is reduced from an optimum. This results in incomplete combustion of the fuel which in turn leads to loss of power and pollution problems. Disclosed in International Application PCT/C A92/00522 is a piston rod and piston connection which addresses the above issue. The upper end of the piston rod is provided with raised portions which engage the underside of the piston crown. As the connecting rod rotates angularly, the piston is caused to move away from the other end of the connecting rod. Similar such mechanisms are disclosed in US Patents 1,431,617, 4,515,441, 2,260,240 and 2,574,934. Object of the Invention It is an object of the present invention to substantially ameliorate some of the disadvantages with prior art piston assemblies or to provide a meaningful alternative to conventional piston and connecting rod design. Summary of the Invention There is disclosed herein a piston and connecting rod assembly for an internal combustion engine, said assembly comprising: a piston having a piston crown; a connecting rod having a piston end and a crank end; and abutting surfaces causing longitudinal movement of said crown portion away from said piston end during relative pivoting of said piston through a predetermined angle relative to said piston end. Brief Description of the Drawings Figure 1 is a schematic sectioned side elevation of a connecting rod and piston; Figure 2 is a schematic sectioned end elevation of the connecting rod and piston of Figure 1; Figure 3 is a cross sectional view of a piston and connecting rod in which bearings are mounted on both the piston end of the connecting rod and on the piston cam surface; Figure 4 is a cross sectional view of the device depicted in Figure 3, along lines 1- l; Figure 5 is a cross sectional view of a piston and connecting rod incorporating a means of retaining the piston according to the teachings of the present invention; Figure 6 is a cross sectional view of the device depicted in Figure 5, along lines 3- 3; Figure 7 is a cross sectional device of a piston and connecting rod according to the teachings of the present invention having a hook-like retainer incorporated into the piston; Figure 8 is a cross sectional view of the device depicted in Figure 6, along lines 5- 5; Figure 9 is a side elevation of the retainer shown in Figures 5 and 6; Figure 10 is a schematic sectioned side elevation of a connecting rod and piston; Figure 11 is a schematic sectioned end elevation of the connecting rod of Figure 10; Figure 12 is a schematic sectioned side elevation of a connecting rod and piston; Figure 13 is a schematic sectioned end elevation of the connecting rod and piston of Figure 12; Figure 14 is a schematic sectioned side elevation of a connecting rod and piston; Figure 15 is a schematic sectioned end elevation of the connecting rod and piston of Figure 14; Figure 16 is a schematic exploded view of a portion of the connecting rod and piston of Figure 14; Figure 17 is a schematic side elevation of a connecting rod and piston; Figure 18 is a schematic end elevation of the connecting rod and piston of Figure 17; Figure 19 is a schematic parts exploded perspective view of the connecting rod of Figures 17 and 18; and Figure 20 is a schematic sectioned side elevation of the connecting rod and piston of Figures 17 and 18. Best Mode and Other Embodiments of the Present Invention In the accompanying drawings there is schematically depicted a piston and connecting rod assembly 10. The assembly 10 includes a connecting rod 11 having a crank end 12 to engage a crankshaft, and a piston end 13. The connecting rod 11 is attached to a piston 14 by means of a gudgeon pin 15 which not only permits angular pivoting movement between the piston 14 and the connecting rod 11, but also longitudinal movement of the piston 14 in the longitudinal direction of the connecting rod 11. This longitudinal movement is permitted by a radial clearance between the pin 15 and piston, or alternatively the pin 15 and the connecting rod. The piston extremity of the connecting rod 11 is provided with a socket 16 having a cavity 17 within which there is received a circular bearing element 18 which may be of a spherical or cylindrical configuration. The piston 14 has a crown 19 beneath which there is located a cam 20 having a cam surface 21. The cam surface 21 has a first portion 22 which leads to a second portion 23. The cam surfaces 22 and 23 engage the bearing element to cause movement of the piston 14 longitudinally relative to the connecting rod 11. More particularly, when the element 18 engages the surface 23, the piston 14 is moved relative to the connecting rod 11. The surfaces 22 and 23 are so shaped that during pivoting movement of the connecting rod 11 through a predetermined angle, the piston 14 will move away from the end 12 of the connecting rod 11. When the assembly 10 is used in an internal combustion engine, and more particularly when combustion is taking place, as the connecting rod 11 is pivoted and moved by the crankshaft, the element 18 moves along the surface 22 to engage the surface 23. This interreaction causes the piston 14 to move away from the end 12. Since the piston 14 during initial pivoting of the connecting rod 11 is moving away from the end 12, the volume of the combustion chamber remains constant despite angular movement of the connecting rod 11. This has two effects, which are firstly, combustion takes place at a higher pressure (due to the volume of the combustion chamber remaining constant or substantially constant) and secondly, the combustion gases are not permitted to expand until the crankshaft is in a better position to receive power from the connecting rod 11. That is there is delayed movement of the piston in response to the pressures generated in the combustion chamber. To prevent movement of the piston 14 longitudinally relative to the connecting rod 11, when such movement is not desired, there is provided a pair of cam followers 24, which are supported by means of shafts 25 received within the passage 26 in the gudgeon pin 27. The cam followers 24 are fixed relative to the connecting rod 11 so as to pivot therewith. The cam followers 24 engage cam surfaces 28. Adjacent the cam surfaces 28 are hollows 29 within which the cam followers 24 project when movement of the piston 14 is to be permitted relative to the connecting rod 11. For example, when the piston is at "top dead centre" the cam followers 29 would begin releasing the piston 14 for movement. This would ensure that at the end of the exhaust stroke the piston would be maintained in its correct position with respect to the connecting rod 11. Yet during a power stroke, the piston 14 would be released, as discussed above, for movement relative to the rod 11. The cam followers 24 would stay engaged with the cam surfaces 28 during each compression or exhaust stroke, and would be located within hollows 29 during the initial part, at least, of each power and intake stroke. This is applicable to a four stroke piston engine. The cam surface 28 would be part of or fixed to the piston skirt 30. The above described preferred embodiment will have the advantages of increased power output as a greater proportion of the fuel will be burnt, and the combustion gases are permitted to expand when the crankshaft is better angularly positioned to be driven by the connecting rod 11. A still further advantage of this preferred embodiment is the minimization of unburnt fuel and the associated reduction in pollution. As shown in figures 3 and 4 there is schematically depicted a piston and connecting rod assembly 40. The assembly 10 includes a connecting rod 41 having a crank end 42 for engaging a crank shaft and a piston end 43. The connecting rod 41 is attached to the piston 44 by a gudgeon pin 45 which not only permits angular pivoting movement between the piston 44 and connecting rod 41 but also longitudinal movement of the piston 14, at least along the long axis 46 of the connecting rod. The piston end extremity of the connecting rod 41 is provided with a socket or cavity 47 within which there is received a bearing element 18 which may be either spherical or cylindrical. The piston 44 has a crown 49 beneath which there is located a cam 50 having a cam surface 51. As explained in the above referenced provisional application, the cam surface 51 engages the bearing element 47 to cause movement of the piston 44 longitudinally relative to the connecting rod 41. As depicted in figures 3 and 4, in some applications it may be advantageous to locate a second bearing 60 on or as part of the cam 50 and cam surface 51. In this way bearing to bearing contact is made between the bearings 47,60. This may have the effect of reducing friction and reducing wear between the surfaces of the piston and connecting rod which are in contact. A means of restraining unwanted longitudinal movement of the piston with respect to the connecting rod are depicted in figures 5-9. It will be understood that during the power stroke of a four stroke engine, the expansive forces within the cylinder promote contact between the longitudinally slidable piston and the connecting rod. However, during the intake stroke, contact between the bearing 48 and the cam 50 may be lost. In order to frustrate clearance between the cam 50 and the bearing 48 a retainer 70 is rigidly suspended below the gudgeon pin 45. This may be accomplished with a series of rigid posts or plates 71. The retainer 70 is preferably a rail or a pair of parallel rails which straddle the connecting rod. As shown more clearly in figure 9 the retainer 70 is contoured with two particular arcuate surfaces 77,72 which cooperate with the contact surfaces 52,53 of the cam 50 to permit longitudinal displacement of the piston, for example during the power stroke while restraining longitudinal movement of the piston and thereby maintaining contact between piston and connecting rod during the intake stroke. To this end, a cylindrical bearing 80 is attached to the connecting rod below the gudgeon pin 45, the contact between the retainer 70 and connecting rod 41 occurring over the surface of the bearing 80. Another method of inhibiting unwanted longitudinal movement of the piston is depicted in figures 7 and 8. In this alternate form of restraint, a second bearing 90 is located above the gudgeon pin 45 on the piston end of the connecting rod 41. A hook¬ like retainer 100 is formed in or attached to the interior surface of the piston 44. The hook-like retainer may be formed as part of the cam 50. The hook-like retainer may comprise a pair of hook-like elements straddling the connecting rod. During the intake stroke, the cylindrical bearing 46 engages the interior surface 82 of the hook-like retainer 81 so that there is no excessive freeplay or longitudinal movement between the connecting rod 41 and the piston rod 44. In Figures 10 and 11 there is schematically depicted a piston and connecting rod assembly 100. The assembly 100 includes a connecting rod 101 having a crank end 102 to engage a crank shaft, and a piston end 103. The connecting rod 101 is connected to a piston 104 by means of a gudgeon pin 105 which not only permits angular pivoting movement between the piston 104 and the connecting rod 101, but also longitudinal movement of the piston 104 in the longitudinal direction of the connecting rod 101. The piston 104 includes a generally cylindrical skirt portion 131 and a crown portion 132. The piston extremity of the connecting rod 101 is provided with a socket 106 having a surface 107 within which there is received a bearing element 108 having an outer surface 109 slidably engaging the surface 107. The bearing element 108 has an upper planar surface 110 which engages a second bearing element 111. The bearing element 111 is engaged within a socket 112 which in turn also has a surface 113 complementary thereto. The surfaces 107 and 109 would be portions of a cylindrical surface. The bearing element 111 has an upper surface 114 which together with the cooperating surface 113 will also be portions of a cylinder. The bearing element 111 has a generally planar surface 115 engaged with the surface 110. The bearing element 111 is slidable in its socket 112. The socket 112 is below the crown portion 132, with the bearing elements 108 and 111 cooperating to lift the crown portion 132 during certain angular positions of the connecting rod 101. As the connecting rod 101 rotates as a result of the action of the crank shaft, the socket 106 moves transversely with respect to the longitudinal axis 116 and due to the socket 106 being spaced from the centre 117, the socket 106 raises the bearing element 108. The bearing element 108 raises the bearing element 111 which in turn raises the crown portion 132. The transverse movement of the bearing element 108 relative to the bearing element 111 is accommodated by the cooperating sliding surfaces 110 and 115. In this regard it should also be appreciated that the gudgeon pin 105 has a radial clearance 118 with respect to the piston end 103 of the connecting rod 101. The bearing elements 108 and 113 during their relative movement, are caused to rotate and slide relative to the abutting surfaces 113 and 106. In Figures 12 and 13 a modification of the assembly 100 is illustrated. In this embodiment, the socket 106 is more offset from the axis 116. Accordingly as the connecting rod 101 rotates, the socket 106 acts as a lever and lifts the crown portion 132 via a bearing element 119. The bearing element 119 is oval in shape so as to have two curved ends 120 and 121. The end 120 is received within the socket 102 while the end 211 is received within a socket 122 formed in the piston 104. The bearing element 119 would angularly oscillate as the connecting rod 107 itself angularly oscillates. In Figures 14 to 16 a still modified form of the assembly 100 is illustrated. In this embodiment, a bearing element 130 is illustrated. The element 130 is received within a socket 131 in the connecting rod 101 however in this instance the socket is generally located about the longitudinal axis 116. The bearing element 130 has a connecting rod end 132 and a piston end 133. The end 133 is received within a socket 134 formed underneath the croWn of the piston. The ends 132 and 133 are arcuate and cooperate with curved surfaces 135 and 136. The bearing element 130 has a central aperture 136 through which a retainer 137 passes to ensure that the bearing element 130 is captively located with respect to the connecting rod 101. As the connecting rod 101 angularly oscillates the bearing element 130 also angularly oscillates to move the piston crown away from the connecting rod. In Figures 17, 18 and 19 there is schematically depicted a piston and connecting rod assembly 140. The assembly 140 includes a connecting rod 141 which connects the piston 142 to the crank shaft of an internal combustion reciprocating engine. The connecting rod 141 includes a pair of guide blocks 143 which are received within circular bearing elements 144. More particularly, each of the bearing elements 144 is provided with an elongated rectangular slot 145. Each slot 145 has longitudinal sides 146 which slidably engage the elongated sides 147 of the blocks 143. However, the guides 143 have a total length (extending in the longitudinal direction of extension of the connecting rod 141) which is shorter than the length of the sides 146. Accordingly, the blocks 143 can move longitudinally along the slots 145 while being engaged by the sides 146. Extending transversely outwardly from the blocks 147 are pins 148. The extremity of the connecting rod 141 is provided with a recess 149 having a surface 150 that conforms to the surface of a cylinder. Located in the recess 149 is a bearing element 151 having an external surface matching the surface 150. The bearing element 151 is freely rotatable in the recess 149. The bearing element 151 has a planar bearing surface 152. The piston 142 has a pair of piston skirt portions 153 and a piston crown 154. The crown 154 has an internal surface 155 provided with an inclined bearing element 156 having a generally planar surface 157. The element 156 is fixed with respect to the crown 154. The surface 152 of the bearing element 150 slidably engages the surface 157. The crown 154 is provided with a pair of threaded passages 159 which are engaged by a pair of threaded fasteners 160. The fasteners 160 attach to the crown 154 a pair of cam members 161. The cam members 161 each have a cam profile 162 including two cam segments 163 and 164 which engage the projections 148. The projections 148 in cooperation with the cam members 161 retain the piston 142 in its correct position to ensure that the piston 142 does not impact against an associated cylinder head, while still permitting movement of the piston 142 away from the crank shaft after the piston 142 passes "top dead centre" . In the above described preferred embodiment, there is substantial area contact between the surfaces 152 and 157 to minimise wear. The surfaces 152 and 157 would be lubricated by oil circulating within the engine. As the connecting rod 141 is angularly displaced relative to the piston 142, the bearing element 150 rotates to accommodate the angular disposition of the piston 142 relative to the connecting rod 141. The bearing element 150 would also slide along the surface 157. Bearing against the flanges 165 are springs 166 which engage the end of the threaded fasteners 167 engaged with the crown 154. The springs 166 are compressed and therefore bias the piston 142 to move in the direction towards the crank shaft. However as the connecting rod 141 moves angularly, the piston 142 is moved away from the crank shaft placing the springs 166 under further tension. The springs 166 in cooperation with the flanges 165 and threaded fasteners 167, ensure that the piston does not move away from the connecting rod 141 at the wrong time and impact against an associated cylinder head. In the embodiments of Figures 18 to 20, the guide- blocks 147, with respect to the apertures 145 would be provided with a clearance 168 to permit the above discussed movement of the guide blocks 143 with respect to the bearing elements 144. The bearing elements 144 permit angular movement of the piston 142 about the axis 169.

Claims: CLAIMS : 1. A piston and connecting rod assembly for an internal combustion engine, said assembly comprising: a piston having a piston crown; a connecting rod having a piston end and a crank end; and abutting surfaces causing longitudinal movement of said crown portion away from said piston end during relative pivoting of said piston through a predetermined angle relative to said piston end. 2. The piston and rod assembly of claim 1, further including a bearing assembly coupling the piston and the connecting rod, said bearing assembly including a first bearing element supporting said piston for angular movement about an axis transverse of said connecting rod. 3. The piston and rod assembly of claim 2, wherein said bearing assembly includes a guide member for guiding the longitudinal movement of said crown portion. 4. The piston and rod assembly of claim 3, wherein said bearing element includes a generally cylindrical surface fixed with respect to said connecting rod, and said guide member is fixed with respect to said surface and engages guide surfaces fixed to said piston. 5. The piston and rod assembly of claim 4, wherein said guide member includes a pair of generally parallel coextensive guiding surfaces, slidably engaged with said guide surfaces. 6. The piston and connecting rod assembly of claim 5, wherein said piston and connecting rod have cooperating portions to operatively prevent said longitudinal movement except during pivoting movement of said piston through said predetermined angle. 7. The piston and rod assembly of claim 6, wherein said cooperating portions include a resilient member operatively extending between said piston and connecting rod to bias said piston to move toward said piston end. 8. The piston and connecting rod of claim 6, wherein said cooperating portions include a cam surface and cam follower. 9. The piston and rod assembly of claim 8, wherein said cam surface is fixed with respect to said piston, and said cam follower is fixed to said guide member. 10. The piston and rod assembly of claim 1, wherein a first one of said abutting surfaces is provided by a bearing element pivotable about an axis generally transverse of said connecting rod, and a second one of said surfaces is generally planar and abuts said first surface. 11. The piston and rod assembly of claim 10, wherein said bearing element is mounted on said connecting rod, and said planar surface is fixed to said piston. 12. A piston and connecting rod assembly, substantially as hereinbefore described with reference to the accompanying drawings.

Inventors: ALLSOPP NEVILLE T, ALLSOPP, NEVILLE, THOMAS
Applicants: ALLSOPP JUDITH O, ALLSOPP NEVILLE T, ALLSOPP, JUDITH, OLIVE, ALLSOPP, NEVILLE, THOMAS
Application year: 1994
Main classification: F02B75
IPC codes: F02B75, F02F3, F16J1